Method and device for producing an absorption silencer

ABSTRACT

The invention relates to a method for producing a shock absorber. A section of a steel wool strip is severed from a supply thereof. The perforated area of a tube is wrapped with the steel wool strip section. Said tube is embedded in sound-absorbing material and accommodated in a housing. The steel wool strip section is severed from the supply thereof by a thermal cut. An appropriate device for carrying out the inventive method comprises a supply station for the steel wool strip ( 6 ), a severing station ( 9 ) for severing individual steel wool strip sections from the steel wool strip supply, a transport station for transporting the steel wool strip and/or the steel wool strip section in the direction (A) towards the tube to be wrapped. Said device also comprises a wrapping station ( 7 ) for wrapping the steel wool strip section around the tube, whereby the severing station ( 9 ) comprises a thermal severing device ( 10 ) for cutting through the steel wool strip ( 6 ).

FIELD OF THE INVENTION

The present invention relates to a method for producing an absorptionsilencer, in which a section of a steel wool strip is severed from asupply thereof, a perforated tube in the area of its perforation beingwrapped with the steel wool strip section, the tube wrapped with thesteel wool strip section being embedded in a sound-absorbing materialand the tube wrapped with the steel wool strip section and embedded insound-absorbing material being accommodated in a housing.

BACKGROUND OF THE INVENTION

Absorption silencers comprise at least one absorption chamber filledwith sound-absorbing material, an exhaustion pipe being connected to theabsorption chamber by way of a perforation. A known problem ofabsorption silencers is the destruction of the sound-absorbing materialby exhaust gas pulsations. In order to protect the sound-absorbingmaterial from being destroyed by pulsating exhaust gas, it is known tocover the exhaust pipe in the region of its perforation with a preformedknitted steel hose or to wrap it with a steel wool strip section. Aknown process of the type described in the opening paragraph ischaracterized in that the individual steel wool strip sections aresevered from the steel wool strip supply during wrapping onto therespective tube. In order to do this, a device intended to perform theprocess is equipped with a “brake”, which, when activated duringwrapping of the steel wool jacket retains the steel wool strip supply,adjoining the contemplated severing point, in such a manner as to causethe steel wool strip to tear. Accordingly, the free end of the steelwool strip section obtained is wrapped onto the tube by continuing thewrapping process.

The known process according to the genus is disadvantageous in more thanone respect. In this context a low process reliability is to beemphasized particularly, i.e. high susceptibility to failure. Inaddition, the relatively high material consumption of steel wool as wellas the necessary time requirement for performing the process are deemeddisadvantageous.

SUMMARY OF THE INVENTION

From this the object is derived forming a basis of the presentinvention, which consists in providing a process of the type set out inthe opening paragraph, proceeding with relatively low materialrequirements and shortened time requirement with a high measure ofprocess reliability.

According to the present invention this object is attained in that thesevering of the steel wool strip section from the supply is performed byway of a thermal cut. A device suited for carrying out the process ischaracterized accordingly in that the severing station serving to severeindividual steel wool strip sections from the steel wool strip supplycomprises a thermal severing device for cutting through the steel woolstrip. This measure alone already causes a distinctly increased processreliability of the method cited in the opening paragraph. Because bysevering the steel wool strip by means of a thermal cut, the loose endsof the severed steel wool filaments of each of the two steel wool stripsections are welded to one another. The result thereof is that in theregion of the end faces of the steel wool strip sections loose ends ofthe steel wool filaments do not project to a significant degree, whichwould result in impairing the transport of the steel wool strip or thesteel wool strip section respectively. On the contrary, the steel woolstrip or, respectively, the steel wool strip sections severed accordingto the present invention by thermal cuts, can be conveyed without anyproblem by means of conventional apparatus. Moreover, as opposed to theknown generic method, neither dust nor short fragments, which may resultin damaging components of the respective device, are formed in thecourse of severing the steel wool strip sections from the steel woolstrip supply. Furthermore, when applying the method according to theinvention, the steel wool strip may be designed both wider and thicker(stronger) than is the case in the state of the art. For in the lattercase the tensile strength to be applied, which increases with the numberof steel wool filaments to be cut, limits both the width of the steelwool strip and its thickness. The possibility provided by the presentinvention to process a wider and/or thicker steel wool strip results ina plurality of other decisive advantages. Accordingly, in the case, forexample, of an appropriately thick steel wool strip, the width of whichis grater than the axial length of the perforated region of the tube,the latter needs to be wrapped with the steel wool strip only two tofour times in order to ensure adequate protection of the sound-absorbingmaterial. This results in a considerably shortened manufacturing processcompared with the state of the art, where, conditional on the use of athinner and narrower steel wool strip, a several times larger number ofwrappings is required. If the steel wool strip used within the scope ofthe hitherto known process is narrower—as is almost always the case—thanthe axial extension of the perforated region of the tube, an axialreversing movement of the steel wool strip is required for wrapping thetube. This results in a compacted configuration of the wrapping jacketof steel wool, i.e. the radial dimension of the steel wool jacket isless in its marginal regions than in the center. This results in anunnecessarily high material consumption while the weight of theabsorption silencer increases unnecessarily. This applies especiallysince the steel wool strips of lesser thickness employed up to now canbe manufactured only with a relatively large tolerance so that forreasons of reliability some additional wrappings have to be performed.In contrast thereto, when employing the present invention, a steel woolstrip of virtually any width and thickness can be processed. Anappropriately thick steel wool strip can be produced at a low toleranceso that additional wraps for increased reliability may be dispensedwith. The fact that the loose ends of the steel wool filaments in theregion of the two end faces of each steel wool strip section are weldedto one another, manifests itself by the way not only during themanufacture of the absorption silencer in question. Also in using theabsorption silencer this feature proves particularly advantageous.Because in this manner the risk of the steel wool strip section beingdamaged by the pulsating exhaust gas in the region of its two end faces,is significantly reduced. This results in a greater serviceable life ofthe absorption silencer in question.

The tube to be wrapped with the steel wool strip section need not,however, have a round cross-section. It may moreover be assembled from aplurality of components and/or comprise added on components. Forexample, even so-called interior baskets and similar hollow bodies maybe considered as “tubes” in the sense of the present invention.

Within the scope of the present invention the steel wool strip sectionmay be severed from the steel wool strip supply before wrappingcommences or after wrapping has commenced. The first mentionedpre-commissioning of the steel wool strip sections is in turn favored bythe problem-free transport of the sections; it results in a furthernoticeable time saving in the manufacturing process of absorptionsilencers.

In a particularly preferred manner severing the steel wool strip sectionfrom the supply is performed by resistance fusion. Accordingly, thethermal severing device comprises a particularly preferred resistancefusion beam, connected to a power supply unit.

Another preferred further development of the invention is characterizedin that the steel wool strip section is fitted to the tube at thecommencement of the wrapping process in the region of its front end—inthe conveying direction—by way of at least one spot weld. Accordingly,the device designed for use within the scope of the process according tothe invention is advantageously characterized in that at least one spotweld electrode is assigned to the wrapping station. In this context aswell it is again of importance that by employing the present inventionsteel wool strips thicker than those of the state of the art may beprocessed. For the steel wool strips of lesser thickness processed inthe past can virtually not be affixed to the tube by spot welding, sincethere is a risk that this would result in a fusing away of thecorrespondingly small number of steel wool filaments.

By means of the at least one spot welding electrode already mentioned,the completely wrapped steel wool strip section may, by the way, befitted to the tube even towards the end of the wrapping procedure in theregion of its rear end—viewed in the conveying direction. This onceagain represents a saving of time as compared with the state of the art,where for the purpose of a mutual mechanical matting or interlocking ofthe steel wool filaments an after-running of several revolutions isrequired, in the course of which a mechanical friction element ispressed against the wrapped steel wool jacket.

The fixation of the steel wool strip section to the tube by way of spotwelding is, however, by no means mandatory. Fixation, for example, bymechanical interlocking by means of needles is also possible.

It has already been pointed out that the present invention permits toselect a width of the steel wool strip greater than the axial length ofthe perforated region of the tube so that reversing of the steel woolstrip to be wrapped is not necessary. This does, of course, not excludethat under certain conditions such a reversing device might be employedafter all. This may, for example, prove advantageous in order to avoidin an individual case, i.e. with a particularly great axial length ofthe perforated region of the tube the special manufacture of an extrawide steel wool strip and to use in its stead an already availablenarrower steel wool strip.

Merely for clarity it may be mentioned in addition that in terms of theterminology of the present invention “steel wool strip” not onlyconnotes a strip of intermatted randomly orientated steel filaments. Onthe contrary, this term also includes such strips made of steelfilaments where the latter take up a preset disposition and orientation,for example, in the form of a knitted or woven structure.

In the following the present invention is elucidated in more detail withreference to [the drawing] FIG. 1. The latter shows in a diagrammaticview a device for severing a steel wool strip section from a steel woolstrip supply and for wrapping a perforated tube of an absorptionsilencer in the region of its perforation with the steel wool stripsection.

DETAILED DESCRIPTION OF THE INVENTION

The device illustrated in the drawing comprises a frame 1. To this isfitted a holding device 2 for a coiled steel wool strip supply 3. A bed4 is provided inside the frame 1. A transport unit 5 is assigned to thesaid bed. The transport unit conveys the steel wool strip 6, unwrappedfrom the steel wool strip supply 3 on the bed 4 towards (arrow A) thewrapping station 7. The latter in turn comprises a motor-driven rotatingreceiving device 8 for the tube to be wrapped.

Inside the frame 1 a severing station 9 is furthermore providedcomprising a thermal severing device 10 including a resistance fusionbeam 11. The resistance fusion beam 11 can be raised and lowered by wayof an associated drive means (double arrow B).

Below the wrapping station 7 a welding unit 12 is provided. Thiscomprises two spot welding electrodes 13. These are driven to bevertically displaceable (double arrow C). These permit the fixation tothe tube of the beginning and the end of the respective steel wool stripsections.

The wrapping station 7 comprises a reversing device—not illustrated—,which, when needed, causes an axial displacement of the steel wool stripsection to be wrapped.

It is apparent from the above description and elucidation of the presentinvention that the principle used in this application can be appliedwith the same or corresponding advantages to other technical fields aswell, where a problem is to be solved, comparable to the one on whichthe present invention is based.

What is claimed is:
 1. Process for the manufacture of an absorptionsilencer, comprising the steps of: severing a section of a steel woolstrip from a supply thereof, wrapping a perforated tube in the area ofits perforation with the steel wool strip section, and embedding thetube wrapped with the steel wool strip section in a sound-absorbingmaterial and accommodating said embedded tube in a housing, wherein thesevering of the steel wool strip section is performed by way of athermal cut, and wherein the steel wool strip section is affixed to thetube by at least one spot weld at at least one of the beginning of thewrapping process in the region of its front end and towards the end ofthe wrapping process in the region of its rear end.
 2. Process accordingto claim 1, wherein the severing of the steel wool strip section isperformed by resistance fusion.
 3. Process according to claim 1, whereinthe tube is wrapped with the steel wool strip section two to four times.4. Process according to claim 1, wherein the width of the steel woolstrip is greater than the axial length of the perforated area of thetube.
 5. Process according to claim 1, wherein the steel wool stripsection is severed from the supply prior to being wrapped onto the tube.6. Device for severing a steel wool strip section from a steel woolstrip supply and for wrapping a perforated tube of an absorptionsilencer in the region of its perforation with the severed steel woolstrip section, comprising: a supply station for the steel wool strip, asevering station for severing individual steel wool strip sections fromthe steel wool strip supply, a transport station for conveying thesevered steel wool strip section in a direction towards the tube to bewrapped, and a wrapping station for wrapping the tube with the severedsteel wool strip section, the wrapped tube being embedded in a soundabsorbing material, wherein the severing station further comprises athermal severing device for cutting through the steel wool strip, andwherein the wrapping station is associated with at least one spotwelding electrode for spot welding the severed steel wool strip sectionto the wrapped tube.
 7. Device according to claim 6, wherein the thermalsevering device further comprises a resistance fusion beam.
 8. Deviceaccording to claim 6, wherein the thermal severing device furthercomprises a resistance fusion beam and wherein the resistance fusionbeam and the at least one spot weld electrode are connected to a powersupply unit.
 9. Device according to claim 6, wherein the wrappingstation further comprises a reversing device for axially displacing thesteel wool strip section to be wrapped.